The main objective of the proposed research is to elucidate the anaerobic metabolism of pectin by human intestinal bacteria. Pectin, a polysaccharide material present in human foods, is extensively metabolized in the intestinal tract, even though the human body does not possess pectin-degrading enzymes. Bacteria that inhabit the human intestine are responsible for the breakdown of pectin. Yet, only very limited information is available about the pathways and enzymatic mechanisms used by bacteria for the metabolism of pectin in the human intestine, or in other anaerobic environments. Specific aims of the proposed research are: i) isolation and identification of diverse strains of pectin-degrading bacteria present in the human intestine; ii) characterization of pectinolytic enzymes produced by representative intestinal isolates; iii) elucidation of anaerobic metabolic pathways functioning in the fermentation of saturated and unsaturated products formed by the pectinolytic activities of human intestinal bacteria; iv) study of physiological interactions between pectinolytic and non-pectinolytic bacteria from the human intestine. Pectin- or polygalacturonate-containing media will be used to select for pectinolytic strains. Purification and characterization of pectinolytic enzymes will involve the use of a variety of protein precipitation, spectrophotometric, and chromatographic techniques. Metabolic pathways will be studied by means of enzymatic assays and other conventional biochemical methods. Interaction studies will involve investigation of physiological activities in co-cultures of pectinolytic and non-pectinolytic isolates. Pectin is a component of dietary fiber. Results of various studies suggest that dietary fiber in human foods plays a role in the prevention of diseases such as colon carcinoma and coronary artery disease. Furthermore it has been found that pectin in the human diet decreases serum cholesterol levels and increases the amount of lipids excreted. These observations indicate that pectin, and the microbial activities responsible for its degradation in the intestine, affect important physiological processes of the human body. A broad understanding of these processes requires information on the metabolic fate of dietary pectin in the human intestine. The proposed research is expected to provide such information.